Biomedical subjects

V Randle

Publications and source records attributed to V Randle.

3 recordsLinked to original sources

PubMed2001

Combined application of electron backscatter diffraction and stereo-photogrammetry in fractography studies.

The main aim of this paper is to report on recent experimental developments that have succeeded in combining electron back-scatter diffraction (EBSD) with stereo-photogrammetry, compared with two other methods for study of fracture surfaces, namely visual fractography analysis in the scanning electron microscope (SEM) and EBSD directly from facets. These approaches will be illustrated with data relating to the cleavage plane orientation analysis in a ferritic and C-Mn steel. It is demonstrated that the combined use of EBSD and stereo-photogrammetry represents a significant advance in the methodology for facet crystallography analysis. The results of point counting from fractograph characterization determined that the proportions of intergranular fracture in C-Mn and ferritic steels were 10.4% and 9.4%, respectively. The crystallographic orientation was determined directly from the fracture surface of a ferritic steel sample and produced an orientation distribution with a clear trend towards the [001] plane. A stereo-photogrammetry technique was validated using the known geometry of a Vickers hardness indent. The technique was then successfully employed to measure the macroscopic orientation of individual cleavage facets in the same reference frame as the EBSD measurements. Correlating the results of these measurements indicated that the actual crystallographic orientation of every cleavage facet identified in the steel specimens is [001].

Journal Article↗

PubMed1999

Crystallographic analysis of facets using electron backscatter diffraction.

Applications of electron backscatter diffraction (EBSD), also known as backscatter Kikuchi diffraction in the scanning electron microscope (SEM) are first and foremost microtexture and grain boundary misorientation analysis on a single polished section in the specimen. A more subtle and revealing approach to analysis of these data is to use EBSD to probe the orientations of planar surfaces, i.e. facets, which bound crystals. These surfaces include: * grain or phase boundaries * fractures * cracks It is of great interest to know the crystallography of such facets since it provides a key to understanding the physical properties of them. As far as investigation methodology is concerned, surfaces or facets associated with polycrystals are of two types: exposed or unexposed. Exposed facets, such as a fracture surface, can be viewed directly in the SEM, whereas unexposed facets, such as a grain boundary, are usually revealed as an etched trace on a polished surface. Photogrammetric methods can be used to obtain the positional orientation of an exposed facet, and the crystallographic orientation is obtained either directly from the surface or by indirect sectioning. Calibrated sectioning is required to obtain the equivalent parameters for an internal surface. The present paper compares the methods for obtaining and interpreting the crystallography of facets, with illustrations from several materials.

Journal Article↗

PubMed1989

Measurement of lattice parameter and strain using convergent beam electron diffraction.

A brief review is presented of the methods of measuring lattice parameters and strain using diffraction techniques. The presence of strain leads to broadening of diffraction maxima, which is normally separable from any broadening caused by size. The special advantages of the convergent beam electron diffraction (CBED) technique is the local nature from which the data are derived. Examples of the use of CBED techniques in measuring lattice parameters and strain are given from studies of precipitation (including misfit measurements) and from investigations of partially recrystallised microstructures. These examples are used to illustrate the advantages and limitations of the CBED technique.

Crystallography↗